Starting from August 6th in 2019, Sentinel-5P TROPOMI along-track high spatial resolution (~5.5km at nadir) has been implemented. For data after August 6th of 2019, please check S5P_L2__CH4___ data collection. The Copernicus Sentinel-5 Precursor (Sentinel-5P or S5P) satellite mission is one of the European Space Agency's (ESA) new mission family - Sentinels, and it is a joint initiative between the Kingdom of the Netherlands and the ESA. The sole payload on Sentinel-5P is the TROPOspheric Monitoring Instrument (TROPOMI), which is a nadir-viewing 108 degree Field-of-View push-broom grating hyperspectral spectrometer, covering the wavelength of ultraviolet-visible (UV-VIS, 270nm to 495nm), near infrared (NIR, 675nm to 775nm), and shortwave infrared (SWIR, 2305nm-2385nm). Sentinel-5P is the first of the Atmospheric Composition Sentinels and is expected to provide measurements of ozone, NO2, SO2, CH4, CO, formaldehyde, aerosols and cloud at high spatial, temporal and spectral resolutions. The retrieval algorithm for Sentinel-5P TROPOMI methane product is a physics based method that uses the Oxygen-A band (760 nm) and absorption bands in shortwave infrared spectrum. In Sentinel-5P/TROPOMI methane algorithm, the atmosphere forward model simulates the absorbing gas (oxygen, methane, water vapor, and carbon monoxide) optical properties, as well as aerosol optical properties with size distribution, refractive index, and number concentration. The inversion is performed based on the forward calculation, the measurement, and the prior information. Cloud filtering is critical in methane retrieval, S5P methane algorithm applies re-gridded Visible Infrared Imaging Radiometer Suite (VIIRS) cloud mask data. Additional cloud filters based on S5P/TROPOMI measurements and the FRESCO apparent surface pressure will be applied when VIIRS cloud data are not available. Other current data filters in the retrieval algorithm include land-only pixels (excluding mountainous areas), spectrum intensity, solar zenith angle and instrument zenith angle. The S5P/TROPOMI methane retrieval is for non-time-critical (NTC) data stream only, and its main outputs include the column averaged dry air mixing ratio of methane, the random error, and the biased corrected dry air methane fraction data based on the retrieved surface albedo. The data are stored in an enhanced netCDF-4 format.